Tuesday, August 5, 2014

Floods and Plant Adaptations

Riparian
zones can be pretty rough places for plant life. Despite readily a
available water supply, the unpredictable, disturbance-prone nature of
these habitats means that static lifeforms such as plants need to be
quite adaptable to survive and persist. Some riparian shrubs and trees
have adopted a "live fast, die young" strategy for survival. They must
be able to cope with things like floods, ice scour, and erosion.
Putting all their energy into quick growth is useful but it also means
that many species, like willows and cottonwoods, have relatively weak
wood. As you may know, these trees are quite prone to breaking. The same
goes for riparian shrubs like dogwoods. After a flood or massive ice
breakup, it is not uncommon to find bits and pieces of these woody
plants strewn all over, usually jumbled up in a log jam somewhere
downstream. Though this may seem disastrous, but looks can be deceiving.

Whereas they all produce seeds, they can also reproduce
vegetatively. This is exactly what you are seeing in this picture. A
willow branch, ripped from its parent plant, has settled downstream into
the mud. Undifferentiated cells under the bark are now producing roots
and stems. In time, this may become a whole new willow tree. Provided
the branches and logs contain enough living material, a new plant can
take root and grow rather quickly. After a heavy flood event, one of
these trees or shrubs can suddenly become multiple clones of the same
individual. Research has even shown that this form of vegetative
reproduction makes for better survival during flood events than that of
seedlings.

Restoration practitioners have taken advantage of
this adaptation as well. One of the quickest and easiest forms of
riparian restoration is the use of live stakes. Live stakes are simply
branches (roughly thumb sized in diameter) cut off from a parent plant
and driven into the ground. Success is best achieved when the plant is
dormant in either early fall or spring. Once the branches awake from
dormancy, they begin growing and entire stream banks can be replanted
over the span of a couple hours with only a handful of volunteers.